In gas appliances and furnaces, diaphragms and/or solenoids are commonly used for controlling the level of gas flow through a gas valve to a burner. Flow-control solenoids typically are actuated by continuous signals from a low-voltage power source. For this reason and for other reasons, valve control via diaphragms and solenoids tends to be complex and costly. In gas fireplace units, gas flow control may be via a stepper-motor-controlled valve, which can vary gas flow without a diaphragm and is powered by intermittent low-voltage signals. Such valves can vary gas flow to vary fireplace flame, but cannot sense outlet flow rate or adjust outlet flow to a desired flow rate value.